[bug] Removed 'Link' from base class

Author: atb00ker

django_netjsongraph/tests/base/test_link.py

@@ -2,7 +2,6 @@
 
 from openwisp_utils.tests import catch_signal
 
-from ...models import Link
 from ...utils import link_status_changed
 
 
@@ -92,6 +91,6 @@ def test_status_change_signal_sent(self):
             link.status = 'down'
             link.save()
         handler.assert_called_once_with(
-            link=link, sender=Link, signal=link_status_changed,
+            link=link, sender=self.link_model, signal=link_status_changed,
         )
         self.assertEqual(link.status, 'down')